SNK Playmore's Metal Slug franchise has been blowing up arcades and sticking it to consoles for years now. The frenetic, run-and-gun, side-scrolling gameplay along with the tongue-in-cheek humor and brilliant 2-D graphics have made this series a fan favorite. While this makes for a great Quarter-eater, it's not a formula that appeals to everyone on consoles (portable or otherwise); these titles sport little depth, feature grueling difficulty, and can be played through in about an hour. Such is the case with Metal Slug XX (pronounced: Metal Slug Double X). The game has all of the conventions and trademarks fans of the series crave, but it isn't a memorable game anyone outside of the core will have more than a passing interest in.

For starters, the game is simply a PSP remake of Metal Slug 7, which released on the Nintendo DS back in November of 2008. After the defeat of General Morden, which occurs after the very first level, a futuristic army comes through a Stargate-like portal and saves their leader-to-be. In order to help Morden realize his "rightful" place as head of the Rebel Army, the Mars People provide the evildoer with advanced weaponry to fight his way clear to another day.

Rather than recounting a new story, Metal Slug XX recycles the narrative told in Metal Slug 7. Of course, if you've ever played a Metal Slug game, that's not really an issue, because you don't play Metal Slug for its plot; you play Metal Slug to rip into enemies with a machine gun and stick 'em with a bowie knife if they get too close. Thankfully, the excellent twitch reflex gameplay is fully intact. Tons of on-screen action in the form of bullets, grenades, helicopters, axes, dynamite sticks, robots, bomb carts, tanks, and a lot more will constantly harry your hero. Jumping to avoid the barrage while unleashing hot death of your own, all while saving POWs, is a satisfying experience for gamers looking for an old-school 2-D challenge.

In terms of challenge, Metal Slug, as always, offers a steep one. To Double X's credit, three difficulty levels are available, along with unlimited continues, so anyone can finish the title (or be brutalized by the CPU; whatever floats your boat). There's a lot of fun to be had in each level of difficulty, but there's no question that Normal is the most balanced. Even still, be prepared to use continues in each and every stage until you improve significantly.

Regardless of the challenge you choose, the Metal Slug XX campaign experience is short-lived. There are only seven levels in all, so you'll play through the story in less than an hour. This is Metal Slug's greatest fault and best feature at the same time. For the vast majority of folks that pick up the title, the game will be too challenging and too shallow to ever get into. For the hardcore set, the short, sweet levels and brutal difficulty make for near endless replayability; trying to get all the POWs on hard is, for all intents and purposes, an impossible feat.

Six classic Metal Slug characters are included out of the box: Marco, Tarma, Fio, Eri, Ralf, and Clark. Each of these characters has special abilities, such as increased pistol firepower, larger grenade capacity, first-shot invulnerability, or even a special melee move. After character death, during the continue screen, you'll be able to switch between any of the available heroes to adjust your strategy according to their unique skills. A seventh character, Leona from The King of Fighters, can be downloaded via the PSN for an extra dollar. She brings the best hand-to-hand skills to the game, but, even at just a buck, picking up the blue-haired beauty feels unnecessary, perhaps a bit like a rip-off. In fact, it seems like making her downloadable was less about making money and more about adding "PSN Support" to the feature set.